Selection Brush

selectbrush

Select an area by painting with a brush.

replace Replace Selection: Replace the current selection with a new selection.
add Add to Selection: Add the new selection to the current selection (or press Shift).
sub Subtract from Selection: Subtract the new selection from the current selection (or press Alt).
intersect Intersect with Selection: Intersect the new selection with the current selection (or press Shift+Alt). This will keep the common areas between the two selections.

Round Brush / Square Brush: Defines the type of brush shape.
Screen Units / Spectral Units: Defines the units used to set the brush shape proportions.
Size: (Screen Units only) Defines the size of the brush in pixels.
Aspect Ratio: (Screen Units only) Defines the aspect ratio of the brush.
Width: (Spectral Units only) Defines the width of the brush in seconds.
Height: (Spectral Units only) Defines the height of the brush in hertz.
Hardness: Defines the hardness of the brush in percents. A hard brush (100%) will have clear edges. A soft brush (0%) will have blurry edges.